Well, a while back I posted with the codes P0446, P0420, and P1300 on my 97 Toy Avalon. I finally got it fixed. The P0446 was a bad solenoid on the canister, P1300 was a bad coil, and P0420 was solved with a spacer.
The mechanic has one of those $6000 laptop computers that helped him get locate which coil/sensor. Makes diagnosis a lot easier. I don't know what type of spacer it is, it is an exhaust spacer...a prefab one from a speed shop.